Hydraulic testing apparatus



w. R. TUCKER EI'AL 2,416,853

HYDRAULIC TESTING APPARATUS March 4, 1947.

Filed Jan. 20, 1944 2 Sheets-Sheet l ///x \g p INVENTORS WARREN K.TUCKER. BY WALTER ERNST;

ATTORNEYS Patented Mar. 4, 1947 2,416,858 HYDRAULIC TESTING APPARATUSWarren R. Tucker, Dayton,

Ohio, assignors Wilmington, DeL, a corpora- Mount Gilead, velopmentCorp., tion of Delaware and Walter Ernst,

to H-P-M De- Application January 20, 1944, Serial No. 518,966

12 Claims.

The present invention relates to testing apparatus for determining thetensile or crushing strength of materials, and more particularly tomachines of this character which are actuated by pressure fluid.

Machines of this general type must be capable of generating high forcesin order to rupture or crush the article being tested and furthermore,such machines must be equipped with suitable instruments for indicatingor'recording the generated forces, from which data the strength of thearticle under test may be com uted. It is obvious that the computedresults of a test will be accurate only if the forces exerted on theworkpiece are accurately indicated or recorded and this represents areal problem in that the position at which the pressure is applied bythe pressure fluid is unusually remote from the surface which appliedthe resultin pressureto the article and inaccuracy in transferring thepressure from one position to the other is often present. Theseinaccuracies may be brcught about by frictional effects between thevarious pistons and the cylinder so that the pressure or force which isactually applied against the article being tested does not represent anexact replica of the pressure or force which is being supplied to theactuating surface by the pressure fluid pump.

The principal object of the invention is to provide an improvedhydraulic testing machine, particularly one in which friction losses areentirely eliminated or at least reduced to a minimum to the end that thepressure which is applied against the primary actuating surface isavailable in exactly the same amount against the actuated or secondarysurface which contacts the article under test.

Another object is to provide a hydraulic ram so constructed that thefrictional losses between the force generated in the main area and theforce applied to the workpiece are negligible so that the latter forceis sensibly the same as that applied to the main area. By accomplishingthis, it is possible to measure the pressure in the main area and fromthat to calculate accurately the force on the workpiece.

Still another object is to provide an improved compression or tensiletesting machine of the hydraulically actuated type wherein thecompression or tensile strength of the test sample can be read directlyon a suitable indicatin gage that is calibrated in pounds per squareinch, compression or tensile strength.

In carrying out these objects we rotate the ram throughout its travel atleast in the testing diequal pressure is applied at both ends of the ramin order to eliminate or equalize any unbalance of internal forces.Thus, the ram is in effect supported on friction-free bearings whichneed carry only the weight of the rotating mechanism.

Accordingly, another object of the invention is to provide an improvedhydraulically actuated testing machine wherein a part of the mechanismfor obtaining power to apply compression or tension to the test sampleis rotated in order to reduce friction, and the mechanism is balancedhydraulically while permitting the rotating effect in order to preventaxial movement of the piston due to an unbalance of forces in thecylinder.

The invention will be better understood when reference is made to thefollowing description and the accompanying drawings in which:

Figure 1 represents a longitudinal sectional view of the improvedtesting equipment.

Figure 2 is a sectional view somewhat enlarged of the apparatus shown inFigure 1 and taken rection and in addition,

along line 2-2 in. that figure, looking in the dicontrolled by a 4-wayvalve rection of the arrows.

Figure 3 is a fragmentary detailed view of a modified form of accessorythat may be employed in the machine shown in Figures 1 and 2.

Figure 4 is a schematic layout of a hydraulic system for operating thetesting apparatus.

' The testing machine of this invention includes a pressure fluid pump Idriven by a suitable electric motor, a hydraulic type of rotatingmechanism indicated generally by the reference character 2 and a testingmechanism 3 hereinafter described. The pump is preferably of thevariable delivery type for continuously supplying fluid under pressureto the testing mechanism so that pressure will be increasingly built upin the testing mechanism gradually to apply increasing pressure to thematerial being tested until the sample breaks or is crushed. A body offluid contained in a reservoir or tank 4 supplies the pump with apressure medium, the latter being 5 of any suitable and well known type.

The testing mechanism 3 includes a heavy cast iron cylinder 6 closed atthe top but open at the bottom to receive a ram or plunger 1 provided ateach end with a grooved piston 8, 9 respectively. The latter extendsupon the open end of the cylinder and is adapted slidably to reciprocatethrough relatively small travel with respect to a surrounding platen ID.The latter is provided with a large counterbored opening II which snuglyreceives the lower piston 9 and has a diametral size exactly the same asthe interior dimension of the cylinder 8. The rain I is provided with apair of shoulders indicated respectively at I2, l3 to provide tworamportions of diiferent diameter from the main portion of the ram. Thepiston 9 may abut the shoulder i2 and it is detachably held in positionby a retaining plate l4, screwed as indicated at l5 to the end of theram. This retaining plate lies flush with the lower surface of thepiston 9.

The open end of the cylinder 5 is held by a cover plate i6 screwed asindicated at I! to the end of the cylinder and has a flange portion l8which extends into the annular recess between the plunger 1 and theinterior of the cylinder. There are a plurality of layers i9 of packingmaterial resting on the flange l8 and this material is held in positionby means of a large split washer structure 20 which sets in an annulargroove formed in the cylinder at a position such as to apply acompressing force on the packing material. Thus, the ram 1 is renderedfluid tight at the position of the packing element.

The platen i0 is mounted for reciprocatory movement on suitablypositioned guides or guide rods 2| and the structure as a whole iscarried on a bed plate or support by means of strain rods (not shown),but which in certain cases may also be constituted of the guide rods 2!.The ram I, including the oppositely disposed pistons 8, 9 is providedwith a longitudinally extending, centrally positioned opening 22 whichin effect serves as a pressure communicating passageway between theupper pressure area and the lower pressure area 24. There is a rod 25bolted at the lower end to the lower surface of the counterbored openingII and at the other end extends through the top of the cylinder into anupstanding cap,

member 26 which has a large interior opening 21 adapted readily toreceive the rod and to accommodate any longitudinal movements thereofwith respect to the cylinder. The upper end of the rod is provided witha squared configuration starting with a position just inside thecylinder and this squared portion is snugly received by a square opening28 in the cylinder, this opening giving a keying effect to prevent anyrotation of the rod 25 with respect to the cylinder. Thus, the platen I0is prevented from rotating and can therefore only slide up and down onits guide rods 2 I. Inasmuch as the opening in the cap member 26constitutes in effect a closed chamber, a confluid which is forcedthrough the square opening 28.

1 duit 29 is provided for draining off any pressure In accordance withone of the features of the invention, the ram 1 is provided withmechanism for rotating the same during its excursions within thecylinder 6 and for this purpose a ring 1 gear 30 is screwed as indicatedat 3i or otherwise secured to the shoulder IS on the ram. The

1 teeth of the gear are illustrated at 32 (Figure 2) and may have aconvolute or any other desired shape. Positioned at opposite sides ofthe circular gear 30 there is a pair of racks 33 of somewhat greaterthickness than the thickness of the teeth 32 for reasons which will beexplained presently, these racks being so arranged that both of them areoperated simultaneously to move the ?gear 30 in one direction or theother depending on the manner in which pressure fluid is introduced intothe actuating cylinder. The racks 33 are secured to the inner sides of apair of reciprocatory cylinders 34 having an interior pressure chamber35. The cylinders are mounted on piston rods 31 having threaded ends, 38whichare received in straps 33 and secured thereto by nuts 40. Theinterior by a closure member 4| so that when pressure fluid isintroduced on either side of the piston 36 and exhausted from the otherside as will be explained hereinafter, the cylinder 34 is caused to movein the horizontal direction and to turn the gear 30 through the rack 33and the gear teeth 32 and thus rotate the ram 1. Pressure fluid isapplied to either side of each piston 35 through conduits 42, 43 whichconnect with pipes 44, 45 respectively of the hydraulic control system(Figure 1).

As shown in Figure 2, the pressure fluid conduit 42 is located to theleft of the upper piston but to the right of the lower piston so thatwhen pressure fluid is introducedinto these conduits in the manner whichwill be described hereinafter, the upper cylinder will be caused to moveto the left and the lower cylinder will be caused to move to the rightsimultaneously.

Conduits 45 and 41 respectively are taken from the cylinder 6 onopposite sides of the upper.

piston 8 for introducing pressure fluid to either Ill. The conduits 44and 48 are connected together and pass into one of the pressure ports ofthe 4-way valve 5,-through a conduit 48. The pressure ram of the valve 5is connected by a conduit 49 to the pump i and the low pressure side ofthe pump is connected through a pipe 50 to the tank 4. A pipe 5| istaken from the tank to the exhaust port of the valve 5. The conduit 41forms a branch of the main conduit 52 and the latter is connectedthrough a hydraulic choke system indicated generally at 53 through theconduit 45. The purpose of the choke system 53 is to provide aregulatable choking effect of the fluid being exhausted from the lowerend of the cylinder 35 but at the same time will permit a full andunobstructive flow of pressure fluid into the lower end of the cylinderduring a different part of the operating cycle.

In general, the choke system comprises a needle valve 54 and a mainvalve 55 which contains a reciprocatory valve'stem (not shown) forcontrolling the fluid opening therethrough. The movement of the valvestem and therefore the control of the size of the opening is dependenton the pressure drop established across the needle valve 54 so that byre ulating the latter valve any desired control of the fluid passingthrough the pipe 45 may be exercised. A variable choke valve of thisgeneral character is illustrated and described in the Farnham Patent2,146,537 assigned to the same assignee as the present application. Inorder to prevent any c oking effect of the pressure fluid flowing intothe lower end of the cylinder a branch circuit 56 containing a one-wayvalve 51 is connected around the variable choke valve.

In operation, the accurately sized test piece is placed under the p atenand the four-way valve 5 is operated to advance the platen. When thelatter engages the work and the pressure builds up, the ram will floatwith equal forces exerted thereon from above and below due to thepassageway 22 which connects the chambers 23 and 24 together, At thistime, the piston 8 moves downward slightly in its bore and rides free ofof the cylinders 34 is closed,

the plate l4. Thus the ring gear 30 moves slightly downward with respectto the racks 33 and for this reason the latter have a greater thicknessthan the ring gear as can be seen in Figure 1. The main cylinderpressure is conducted through the conduit 44 to each of the cylinders 34so that pressure fluid in effect is introduced to the left of the upperpiston 36 (Figure 2) and to the right of the lower piston, causing theirrespective cylinders to move to the left and right respectively. This inturn serves to rotate the ring gear 30 counter-clockwise, thus turningthe ram 1 and its terminating pistons 8 and 9. The fluid which ispresent on the low pressure side of each of the pistons 36 is exhaustedthrough one or more conduits 45 and through the variable choke valve 53into the conduit 52 which also receives fluid exhausted from the lowerside of the piston 8 through the conduit 41. This exhaust fluid is takenthrough the 4-way valve 5 back to the tank 4. The choked outletrepresented by the variable choke valve 53 serves the purpose ofpreventing too rapid rotation of the ram 1 in order that the workingstroke of the platen l may be completed before the cylinders 34 reachthe end of their respective strokes and the rotation of the ram ceases.

On the retraction stroke, push back pressure fluid is admitted to thelower side of the piston 8 through the conduit 41 by reversing the 4-wayvalve and this fluid is also admitted to the right hand side of theupper piston 36 (Figure 2) and the left hand side of the lower pistonthrough the by-pass valve 51 and through the conduits 31 so that theupper and lower cylinders (Figure 2) are caused to move to the right andleft respectively in order to rotate the ring gear clockwise. Inasmuchas there is no particular need on the up stroke of the pistons 8, 9 tomake sure that the rotary action of the ram 1 carries all the way fromthe lower limit of travel of the ram to the upper limit, it is notnecessary to provide a variable choke valve in the conduit '55. As wasexplained hereinbefore, it is only on the down stroke of the ram thatthe variable choke valve structure 53 becomes really necessary as it isduring this part of the operation that the test is taking place.

During the clockwise movement of the ram the latter is forced upwardlyby the pressure fluid acting on the lower surface of the piston 8 andthe exhaust fluid from the compartment 23 goes through the conduits 46,48 through the valve 5, conduit 5| to the tank. The retraction sides ofthe pistons 36 of the cylinders 34 are also exhausted through theconduit or conduits 44 and the valve 5 to the tank. As the ram 1 movesupwardly, the lower piston 9 picks up the platen In by means of theplate l4 and carries it upwardly with the ram.

By rotating the ram during the working stroke nearly all of the frictionbetween the pistons 8, 9 and the interior wall of the cylinder 5 iseliminated. Consequently, a pressure gage in communication through aconduit 59 with the upper pressure chamber 23 will represent a trueindication of the force exerted on the workpiece which is positionedimmediately below the platen II). In

fact, the gage 58 may be calibrated directly in pounds of force ratherthan pressure. It will be noted that the ram and its two oppositelydisposed pistons 8. 9 in effect float within the cylinder 6 due to theadmission of the same pressure in each of the chambers 23 and 24. It hasbeen pointed out that the pressure areas in these chambers are exactlyequal that the integral forces acting on the respective pistons arecoinpletely balanced and there is no tendency for any axial movement ofone or both of the pistons with respect to the cylinder due to anyunbalance of forces within the cylinder, The force which acts againstthe platen If] within the compartment 24 is exactly the same as theforce which acts against the upper surface of the piston 8, which inturn is accurately measurable by the gage 5B.

The square topped rod 25 obviously serves to prevent any rotationalmovement of the platen I0, thus again assuring that all of the forces indicated by the instrument 58 operate solely in the longitudinaldirection and these indications represent the actual downward forcebeing exerted by the platen ID on the test sample. Other ways may beemployed to prevent rotation of the platen Ill and in Figure 3 there isshown a roller 60 with an arcuate peripheral surface mounted on a stud6| which is secured to the platen. The roller may bear against a guiderod 2| and if desired as many rollers may be provided as there are guiderods, Thus, the rollers permit the platen to move upwardly or downwardlyalong the guide rods and at the same time provide suflicient contactwith the guide rods as to prevent any rotational movement between theplaten and the cylinder 5, thus again insuring that none of the energywhich serves to move the ram 1 downwardly or to rotate the ram isdissipated by a rotational movement of the platen.

From the foregoing it is evident that we have disclosed an improved formof a testing machine of the hydraulically operated type in which theforces acting on the platen through a double piston form of ram may beaccurately measured by an indicator. This ram is of the floating typeand we have provided structure by which the ram can be simultaneouslyrotated throughout the entire testing operation, thus assuring thecomplete elimination of friction and therefore a strict accord betweenthe measurable force acting on the ram and the actual force exerted bythe platen on the test piece.

It will be understood that we desire to comprehend within our inventionsuch modifications as come within the scope of the claims and theinvention.

Having thus fully described our invention, what we claim as new anddesire to se ure by Letters Patent is:

l. A hydraulic press comprising a first stationary cylinder and a secondmovable cylinder, bores of equal diameter in said cylinders, a plungerhaving equal opposite end areas disposed within said bores, anunrestricted fluid communication between said areas, means forpreventing relative rotation of said cylinders while permitting freerelative axial movement thereof, hydraulic motor means arranged torotate said plunger and cylinders relatively, a fluid source, a valvemovable to connect said source with said areas and also with said motorfor simultaneously urging said cylinders to move relatively axially andto move said plunger and cylinders to rotate relatively, and flowcontrolling means operable automatically for maintaining the speed ofsaid motor means and, therefore, the rate of said relative rotation at apredetermined value.

2. A hydraulic press comprising a first stationary cylinder and a secondmovable cylinder, the latter acting as a platen for exerting force on aworkpiece, said cylinders having bores of equal diameter therein, aplunger having equal 1 er with respect to each opposite end areasdisposed within said bores, said areas being interconnected by anunrestricted passage in said plunger, a gear connected with saidplunger, a rack meshing with said gear, a hydraulic motor connected toactuate said rack for rotatin said plunger relatively to said cylinders.a retracting area on said plunger in one of said cylinders. a source offluid under pressure, a valve movable simultaneously to connect saidsource with one of said end areas and with one end of said hydraulicmotor or to connect said source with said retracting area and with theother end of said motor, and means for controlling the rate of fluidsupply to the said one end of said motor and for permitting the freesupply of fluid to the said other end thereof.

3. In a hydraulic press, a cylinder, a plunger having a main advancingarea and a retracting area reciprocable in said cylinder, a platen, a,bore in'said platen, a piston on the end of said plunger for beingreceived in said bore and having an area substantially equal to the mainarea of said plunger, means affording unrestricted fluid communicationbetween said main area and the bore in said platen, means for preventingrelative rotation of said platen and cylinder while permitting freerelative axial movement thereof, hydraulic motor means arranged torotate said plunger relative to said cylinder and platen, a, source offluid under pressure, a, valve movable to connect said-source with saidmain area and with one end of said motor means or to connect said sourcewith said retracting area, and

with the other end of said motor means, and valve means seriallyconnected with said motor means operable to control the supply of fluidthereto when said source is connected with said,

main area and to thereto when said retracting area.

4. A hydraulic press comprising a movable platen for applying pressureto materials and having a cylinder bore therein, a stationary cylinderhaving a cylinder bore of equal diameter to that in said'platen, aplunger having a pair permit the free supply of fluid source isconnected with said of said pistons extending into said cylinder toform-work producing and retraction chambers 45, of opposed pistons Ofequal surface areas, one

therewith and the other of said pistons extending into the bore in saidplaten to form a work tending through said plunger and continuously iand unrestricted interconnecting said work producin'g chambers, meansfor rotating said plungof said cylinder and platen when pressure fluidis introduced into any one of said chambers for eliminating frictionbetween the pistons and said cylinder and platen, and

means for alternately introducing fluid under 1 pressure into said worki said retraction chamber.

producing chambers and 5. A hydraulic press comprising a'stationarycylinder and a movable platen having cylinder ,bores of equal diametertherein, a plunger extending between said bores and having a pair ofopposed pistons of equal size thereon which form with the bore in saidcylinder working and retraction chambers and with the bore in said plat-,en a Working chamber, an unrestricted passagethe retraction chamber.

6. A hydraulic press comprising a cylinder and producing chambertherewith,'a passageway exa hollow platen, a plunger extending betweenthe interior area of said cylinder and platen and having a pair ofopposed pistons of equal size thereon which form with said cylinderworking and retraction chambers and with said platen, a working chamber,passage means extending between said working chambers for continuouslymaintaining said plunger in a state of balance due to equal pressuresbeing applied to said pistons at the opposite ends thereof, means foralternately introducing fluid under pressure to said working chambersand said retraction chamber, and means for rotating said plungerrelative to each of said cylinder and platen when fluid under pressureis introduced into said working chambers in order to eliminate frictionbetween the pistons and each of said cylinder and platen.

7. A hydraulic press comprising a cylinder and a hollow platen, aplunger extending between the interiorareas of said cylinder and platenand having a pair of opposed pistons of equal area which form with saidcylinder working and retraction chambers and with said platen aworking'chamber, a passageway continuously interconnecting the Workingchambers whereby fluid pressures therein are always equal and saidplunger is always in the state of balance with respect .to the saidpressures, means for alternately introducing fluid under pressure tosaid working chambers and said retraction chamber, and means forrotating said plunger with respect to each of said cylinder and platenwhen fluid under pressure is introduced into said working chambers toeliminate friction between said pistons and said cylinder in platen, thesaid means comprising a gear and a rack structure associated with saidplunger and a hydraulic motor for operating said structure in unisonwith the operation of said plunger.

8. A hydraulic interior areas of the cyl nder and platen and having apair of opposed pistons of equal size on the opposite ends thereof oneof which forms with said cylinder working and retraction chambers andthe other of which forms with said platen aworking chamber, a passagewaycontinuously connecting said work'ng chambers for maintaining thepressures therein equal at all times, means for rotating a plunger withrespect to each of said cylinder and platen when pressure fluid isintroduced into said working chambers to eliminate friction between saidpistons and said cylinder and platen. said means comprising agear'secured to said plunger, a, rack meshing with said gear, ahydraulic motor connected to actuate said rack, and a valve movable forapplying pressure fluid to saidworking chambers simultaneously with theapplication of presfor applying pressure fluid simultaneously to saidend areas of said plunger in order to move said platen with respect tosaid cylinder and also to maintain the plunger in a state of axialpressure balance, means responsive to the supply of pressure fluid tosaid end areas for rotating said plunger with respect to each of saidcylinder and platen, and means connecting said platen and cylinder andpreventing relative rotation thereof press comprising a cylinder andwhile permitting free relative movement thereof axially.

10. A hydraulic press comprising a platen and a cylinder which aremovable axially with respect to one another but are prevented frommoving rotatably with respect to one another, a plunger having a pair ofopposed pistons, one of said pistons extending into said cylinder toform working and pull back chambers and the other piston extending intoa cylinder bore in the platen to form a working chamber, said workingchambers being in continuous and unrestricted communication with oneanother, means for rotating said plunger with respect to each of thecylinder and platen comprising a gear connected with said plunger, areciprocating hydraulic motor, a rack actuated by said motor andengagingsaid gear, a valve movable into a first position to. supplyfluid to one end of said motor and to said working chamber and into asecond position to supply fluid to the other end or said motor and tosaid pull back chamber, and means of controlling the rate of movement ofsaid motor during at least the supply of fluid to said working chamber.

11. A hydraulic press comprising first and second cylinders having bores01 equal diameter therein and movable relatively axially, a plungerhaving equal opposite end areas disposed within said bores and having aretracting area in one of said bores, hydraulic motor means arranged torotate said plunger and cylinder relatively, means for simultaneouslysupplying equal fluid pressures to said end areas for urging saidcylinders to move relatively axially and for supplying a controlledquantity of pressure fluid to said motor means for relatively rotatingsaid plunger and cylinders at a controlled rate, and means of supplyingpressure fluid to said retracting area for returning said cylinders totheir initial relative position.

12. A hydraulic press comprising, a stationary cylinder, a movablecylinder for acting asa platen, said cylinders having equal borestherein, a plunger having equal opposite end areas disposed within saidbores and having a retracting area in one of said bores, hydraulic motormeans arranged to rotate said plunger and cylinder relatively, means forsimultaneously supplying equal fluid pressures to said end areas forurging said cylinders to move relatively axially and to said motor meansfor relatively rotating said plunger and cylinders, or to saidretracting area and to said motor means to return said cylinders andplunger, and means operable during the first mentioned supply ofpressure to said cylinders for controlling the rate of movement of saidmotor means.

WARREN R. TUCKER. WALTER. ERNST.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED s'ra'rrzs PATENTS

